Question 17 is based on the passage you have just heard.

听力原文

        Pigs are not native to North America. They were first introduced to California by Spanish and Russian explorers and settlers many centuries ago. (16) [In the early times, pigs were allowed to wander freely in search of food. This practice also allowed many pigs to escape from farms and live in the wild, which became a problem.] In fact, they’re one of the most damaging invasive species on the continent. Wild pigs cause millions of dollars in crop damage yearly. (17) [They also harbor dozens of diseases that threaten both humans and farm animals.] Forest patches with wild pigs have been found to have considerably reduced plant and animal diversity. In addition to either eating other animals or their food supply, wild pigs damaged native habitats by rooting up grasses and rubbing on trees. Their activities may also create opportunities for invasive plants to colonize these areas. Wild pigs will eat almost anything containing calories. Mice, deer, birds, snakes and frogs are among their victims. They can also harm other wild species through indirect competition rather than eating them or shrinking their food supply. On one particular United States island, wild pigs themselves became an attractive food source for a species of mainland eagle. (18) [The eagles began breeding on the island and also feeding on a species of native fox. The foxes were almost wiped out completely.]

17. Why are wild pigs a threat to humans? （为什么野猪会对人类构成威胁？）

解析：D。录音前半部分提到，野猪身上藏匿着几十种威胁人类和农场动物的疾病。D项与此内容相符，其中carry a great many diseases是对录音中harbor dozens of diseases的同义替换，故为正确答案。

错项排除：A项和C项在录音中无依据，故均排除。B项利用录音中出现的food supply设置干扰，但这里说的是野猪猎食其他动物及其食物，这是对植物和动物多样性的破坏，而不是对人类的威胁，而且也不等同于破坏了食物供应链，B项不符合题意，故排除。